modified acrylics dental material

1. Modified
Heat-cured Acrylics
1. Microwavable acrylic
2. Rapid-cured acrylic
3. High impact strength acrylic
4. Fiber-reinforced acrylic

2. Rapid-cured acrylic
 An altered initiator that allows denture base
processing in boiling water for only 20 min.
Advantages
 Rapid curing with minimal porosity
Disadvantages
 High % of residual monomer (3-7 times > Conv. HCA)
 Lower mechanical properties
 Porosity of bases ≥ 6mm thick

3. High impact acrylic
 Powder is a graft copolymer of PMMA - butadiene
rubber
 2 formats of polymer beads are exist
 No cross-linking is added to the composition
Is better than
Because it produces better dough
characteristics
Rubber
Acrylic
Rubber
Acrylic

4. Advantages
 High impact strength
 Low crazing rates
 Low residual monomer contents
 Good attachment to art. Teeth and good fit
Disadvantages
 Expensive
 Reduced stiffness
High impact acrylic

5. Fiber and
metal- reinforced acrylic
 Certain fibers (Carbon, glass, Kevlar, Polyethylene) and
metal fillers (Zerconia and alumina) are incorporated in
acrylic powder
Drawbacks
 Carbon fibers cause black discoloration
 Glass fibers are irritating and could injure soft tissues
 Kevlar fibers complicate the packing process and gives
straw color
 Polyethylene fibers is promising
 Adding metal fillers ↓ poly. Shrinkage but deteriorates
the properties

6. Chemically-cured
Acrylics
 A chemical compound ( 3ry amine
Activator) is added to the monomer
composition to activate the initiator
 An activator paste (P-toluine sulphonic
acid) could be added to the regular acrylic
to activate the polymerization at room
temperature

7. Characters of
the chemically-cured acrylic
 Polymer beads have lower mol. wt.
 Liquid contains chemical activator (3ry amine) to start
the polymerization at room temp.
 The material provides;
1. lower degree of polymerization
2. Lower mechanical properties
3. Higher % of residual monomer
4. Higher rate of porosity
5. Higher rate of water sorption
6. Lower color stability
7. No thermal shrinkage
8. Oversized dentures (+ 0.3-0.4%)

8. Characters
of the chemically-cured acrylic
 Practicability
1. Short processing time (10-15 min)
2. Complete polymerization occurs at room temp in 3 hrs
3. Both compression molding or fluid resin techniques
could be used to fabricate denture bases
Applications:
- Denture base (temp &permanent)
- Repair of broken dentures
- Special trays

9. Fluid resin technique

10. Light- cured
Acrylics
The BVL is used to activate the
photo-sensitive initiator named
Comphroquinon
The material is a composite structure
Usually present as sheets or robs in
light-proof pouches

11. Characters
of the light-cured acrylic
Composition: Composite Paste made of
 Matrix of UDMA and PMMA
 Microfine silica fillers
 Organic fillers (Prepolymerized polymer beads)
 Photoinitiator
The material provides;
1. No MMA monomer is present (no allergy)
2. Lower physical and mechanical properties
3. Lower rate of polymerization shrinkage
4. Better fit

12. Applications
 Denture base
 Repair of broken prostheses
 Special trays
Denture construction
 No flasking is required
 Adaptation of sheet material over the cast to
form the denture base  light curing for 5 min
 Artificial teeth are then seat over the rob material
 light curing for another 5 min
Characters of
the light-cured acrylic